Obviously the R-PI doesn't have a Centronics parallel LPT: (printer) port, but just like there are USB to RS232 (COM: port) adapters there are also USB to LPT: port adapters. It a basic feature of the USB standard to support /replace "legacy devices".

Also some HD44780 based LCD displays fashion a i2c interface already. I plan to go with the PCF8574P.You have to run the PCF8574P and the LCD display with 3.3V. A 5V LCD should work if the IOs are 3.3V compatible.

This board makes it slightly simpler to wire the LCD to the RPI's pinheader, because it converts the signals to a more manageable form, one that bitwizard has expansion boards for. That is almost all it does.

I'm not sure if the people from bitwizards read this, but kudos ("goed gedaan hoor") for your work.Perhaps an I2C RTC board, and maybe a RS232 driver board to a DB-9 connector might be popular items.

And perhaps a better name for the "Raspberry serial BOB board", perhaps "raspberry breakout board to expansion boards" describes it functions better, I thought this name was slightly confusing.

UncleDave wrote:Out of complete ignorance.......why not connect a LCD panel directly to the GPIO pins?

UD.

It can be done with suitable level shifting, but the Pi's I/O is 3.3volt and most LCD modules are 5volt.That's why you can't directly connect an LCD to the Pi's GPIO - I am assuming you are referinf to parallel connection.Texy

I don't think you need the level-shifters since you usually only send from the Pi to the LCD and don't need to read any data coming from the display. And most 5V-pins will read 3.3V as a logical "1" so it might just work. But don't blame me if you fry anything while trying

jannis wrote:I don't think you need the level-shifters since you usually only send from the Pi to the LCD and don't need to read any data coming from the display. And most 5V-pins will read 3.3V as a logical "1" so it might just work. But don't blame me if you fry anything while trying

Yes jannis, you are right. One can perfectly attach a 5V LCD directly to the GPIO ports. I have quickly done so recently

jannis wrote:I don't think you need the level-shifters since you usually only send from the Pi to the LCD and don't need to read any data coming from the display. And most 5V-pins will read 3.3V as a logical "1" so it might just work. But don't blame me if you fry anything while trying

Yes jannis, you are right. One can perfectly attach a 5V LCD directly to the GPIO ports. I have quickly done so recently

lcd.jpg

I assume that you were able to communicate with the LCD. Are you willing to share what you did and how with us?

1. I soldered GND, VB0 (Backlight Ground) and V0 (Contrast Adjustment) of the LCD to the GND pin of the Raspi.2. I soldered Vcc (Supply voltage of the whole module) to the pin labeled 5V03. I then soldered VB1 (Backligt Supply Voltage) to GPIO18 so I can turn backlight on/off programmatically. Of course you can also use Vcc or not even attach it at all4. I then soldered R/W of the LCD to GND in order to have it in write mode all the time and then wired RS (register select) to GPIO24 and E (enable, the pulse which tells the LCD to read the values on the datalanes) to GPIO235. Finally I soldered DB4 to GPIO4, DB5 to GPIO15, DB6 to GPIO21 and DB7 to GPIO22. The other pins have been intentionally left free. I accessed the screen in 4-bit mode to save some wires6. My source code at http://pastie.org/3954992 was then basically created using the example on the wiki & some googling.

PS: Of course i did not solder the cables directly to the Raspi but to a connector i had lying around

1. I soldered GND, VB0 (Backlight Ground) and V0 (Contrast Adjustment) of the LCD to the GND pin of the Raspi.2. I soldered Vcc (Supply voltage of the whole module) to the pin labeled 5V03. I then soldered VB1 (Backligt Supply Voltage) to GPIO18 so I can turn backlight on/off programmatically. Of course you can also use Vcc or not even attach it at all4. I then soldered R/W of the LCD to GND in order to have it in write mode all the time and then wired RS (register select) to GPIO24 and E (enable, the pulse which tells the LCD to read the values on the datalanes) to GPIO235. Finally I soldered DB4 to GPIO4, DB5 to GPIO15, DB6 to GPIO21 and DB7 to GPIO22. The other pins have been intentionally left free. I accessed the screen in 4-bit mode to save some wires6. My source code at http://pastie.org/3954992 was then basically created using the example on the wiki & some googling.

PS: Of course i did not solder the cables directly to the Raspi but to a connector i had lying around

The compiler warnings seem to be "ok" to me. I get the same when I compile with -Wall option.

So, now at least you know that you wired the backlight correctly

A few troubleshooting hints I can give you are:Once you have attached the LCD and booted the Raspi, but not yet run the program the LCD module should show a line of black "bricks" - If you cannot see the bricks you'll have to double-check VCC and GND. If they are OK, check the contrast pin - eventuall you'll have to use a potentiometer instead of soldering it to GND.

Should the LCD still show the "bricks" after running the program, there is something wrong with the initialization-sequence and you'll have to double-check the data-lanes. Also make sure you wired R/W to GND.